interface Person2 {
    readonly id: number,
    name: string
    [propName: string]: any  // 任意属性
}
let P2:Person2 = {
    id: 1,
    name: 'zhang',
    age: 25
}
// 接口继承
interface  parentInterface {
    say(): void
}
interface childInterface extends  parentInterface {
  sayHello (): void
}
class Person1 implements childInterface {
    say() {
        console.log('say')
    }
    sayHello () {
        console.log('sayHello')
    }
}